“Mule” and “buck” are old-fashioned names for a family of mixed drinks that include ginger ale or ginger beer and lime or lemon juice.

Adding lime to a Dark ‘n’ Stormy creates a Rum Buck (also called a Jamaica Buck or a Barbados Buck). You can have a Gin Buck (a.k.a. London Buck), a Bourbon Buck (Kentucky Mule), a Tequila Buck or a Whiskey Buck.

A buck is the male of a number of different animals, including the antelope, deer, goat, hare, mule, rabbit and sheep.

Buck cocktails have been around for as long as ginger ale. The Gin Buck was a popular summer cooler during the Roaring Twenties (1.5 ounces gin, 4 ounces ginger ale, juice of half a lemon or lime).

The Moscow Mule was invented in 1941 by John G. Martin of G.F. Heublein Brothers, Inc., a spirits distributor; Rudolph Kunett, president of Heublein’s vodka division; and Jack Morgan, President of Cock ‘n’ Bull Products (which produced ginger beer) and proprietor of a restaurant of the same name, on Sunset Boulevard in Los Angeles.

According to one citation, the three friends were in the Chatham Hotel bar in New York City, and wondered what would happen if a two-ounce shot of vodka—then a relative novelty in the U.S.—was combined with ginger beer and lime. Four or five drinks later, the new cocktail was christened the Moscow Mule. (Source: Wikipedia)

The name “Moscow” was conferred in honor of the vodka. In terms of why “Moscow Mule” instead of “Moscow Buck”: We can only imagine that they liked the alitteration.